To put that into perspective, the elevation of Denver, Colorado is one mile (5,280 feet, 1,609 meters) above sea level while Mount McKinley in Alaska claims the highest elevation in the United States at 20,320 feet (6,194) meters.

Our bodies undergo several common physiological changes at altitude. These include:

Deeper and/or faster breathing

Shortness of breath (especially during physical activity)

Changes in nighttime breathing

Increased urination

Symptoms of altitude stress include headaches, nausea, crabbiness and disrupted sleep. Though unpleasant, these are easily tolerated by most people at altitudes of up to 8,000 feet (2,438 meters). To avoid or ameliorate the effects of altitude, it's important to acclimatize yourself. We talk about that next.